Scott,
An interesting set of events / conditions. As I had had good results with Ultimate on a Pentium 4 630 which was in the first batch of 64-bit Xeons, it seemed that the two or three generation more advanced xw8600 should not be troublesome.
Having upgraded several worstations from XP and Vista, my prefernce has been fro Professional also as I didn't really use the security, capacities, and network enhancement of Ultimate anyway. However, if MS felt that the Windows 7 equivlaent of Vista Business is Ultimate, they should know.
For our friend Rhothgar, who has a case of Windows fatigue - haven't we all at some pont- it seems the easiest first solution would be to try a repair install of Ultimate. That might quickly restore Boot Manager and thereby forestall having to obtain another copy of Windows. Because the installation was not tried after a reformatting, that, plus an upgrade of BIOS would be next easiest as, again, it doesn'r involve negotiating a new version of Windows.
Cheers,
BambiBoomZ